I want to make some measurements of a amateur recording studio of a friend of mine. The room is the usual rectangular format. I'm not worried about sound insulation but more about the modal behaviour of the room and the sound decay within it.

OK, so my first thought about checking the modal behaviour was to place a loudspeaker in a corner or the room (since it's the junction of 2 walls and the floor) and the microphone on the opposite corner, also near the floor. The loudspeaker I presume should be pointing towards the mic.... (hope I'm correct on this)

Does it justifies to use more then one loudspeaker to excite the room ( to excite different kinds of modes ? )

Regarding the calculation of EDT and T60 which are the most common mic placements for a small recording studio (talking about the room where the sound is capture, not the control room, not sure if I was explaining myself well).

I presume the sound source will stay in the corner in order to fully excite the room, correct ?